As the _Sea Hound_ streaked alongside the Flying Lab, two figures in the seacopter's flight compartment waved to Tom and Bud. One was Hank Sterling, the blond, square-jawed chief pattern-making engineer of Enterprises. The other was husky Arv Hanson, a talented craftsman who transformed the blueprints of Tom's inventions into working models. "All set," Hank radioed. "Lead the way." "Roger!" Tom replied. Flying at supersonic speed, they reached the area of the lost missile in the South Atlantic soon after lunch. Already on hand were ships of the Navy task force assigned by Admiral Walter to participate in the missile search. The _Sea Hound_ settled down on the surface of the water, while the _Sky Queen_ hovered at low altitude nearby. Tom contacted the government craft and learned that as yet no sign of the lost Jupiter prober had been detected. Then he made ready to begin his own search. "Let's try the Fat Man suits first," Tom told Bud. Turning to Slim Davis, a Swift test pilot who was in the crew, the young inventor added, "Take over, will you, Slim?" "Righto." Slim eased into the pilot's seat. "Got a job for me, skipper?" asked Doc Simpson, Swift Enterprises' young medic. "Yes. Help the boys, if you like, rig the undersea elevator, and then assemble a tractorized air dome," Tom suggested. "Will do," Doc promised. A ladder was dropped. Tom and Bud excitedly descended to the _Sea Hound_. The search for the lost missile was about to begin! Once the boys were aboard, the seacopter submerged and dived quickly to the ocean floor. Tom and Bud each climbed into a Fat Man suit and went out through the air lock. The suits, shaped like huge steel eggs with a quartz-glass view plate for the operator seated within, had mechanical arms and legs. The boys waddled about, the built-in searchlights of their suits piercing the murky gloom. They saw nothing but the deep accumulation of silt on the ocean bottom, which made the going difficult. "This is too slow," Tom called over his sonarphone. "Let's try the air dome." The dome was a huge underwater bubble of air, created by a repelatron device which actually pushed the ocean water away. The air supply inside was kept pure by one of Tom's osmotic air conditioners which made use of the oxygen dissolved in the water. The air bubble, however, even with its jet-propelled platform, also proved inadequate for the research job. Its caterpillar treads repeatedly bogged down in the silt. "Maybe the seacopter itself is our best bet," Bud suggested. "Worth a try," Tom urged. But the _Sea Hound_, too, had a serious drawback. Even with its powerful search beam sweeping the ocean floor as it prowled along, the explorers found their vision too limited. Finally Tom said, "Bud, we could skin-dive at this depth." "Let's give it a whirl," Bud urged.